Deterministic Symmetry Breaking of Low-Dimensional Plasmonic Nanostructures: Assembly and Plasmonic Response

The physical properties of matter rely fundamentally on the symmetry of constituent building blocks. This is particularly true for structures that interact with light via the collective motion of their conduction electrons (i.e., plasmonic materials), where the observation of exotic optical effects, such as negative refraction and electromagnetically induced transparency, require the coupling of modes that are only present in systems with nontrivial broken symmetries. Lithography has been the predominant fabrication technique for constructing plasmonic metamaterials, including those with broken symmetry. In this work, we show that low-symmetry plasmonic structures can be assembled using DNA as a programmable surface ligand. The optical properties that arise are a result of systematic symmetry breaking and demonstrate the appearance of π-type coupled modes formed from both dipole and quadrupole nanoparticle sources. These results demonstrate the power of solution-phase assembly for generating unusual structures that exhibit both fundamentally insightful and technologically important optical properties.